The present invention relates generally to compositions and methods for the treatment of insomnia and related conditions. The invention is more particularly related to controlled-release sedative-hypnotic compositions with particularly short half-lives, and methods for using such compositions to promote rapid sleep onset and sleep maintenance.
Many physiological functions are characterized by diurnal rhythms, in which levels of circulating hormones, catecholamines and other compounds fluctuate during the day and/or night. Certain medical disorders, such as insomnia, are associated with abnormalities in these rhythms. The time, within a 24 hour period, of administration of drugs for the prevention and treatment of such disorders can be a critical factor in determining efficacy of the therapy.
The term xe2x80x9cinsomniaxe2x80x9d refers to the perception of inadequate or non-restful sleep by a patient. Insomnia is a frequent complaint, reported by 32% of the adult population surveyed in the Los Angeles area (Bixler et al, Amer. Journal of Psychiatry 136:1257-1262, 1979), and 13% of the population surveyed in San Marino, Italy (Lugaresi et al., Psychiatric Annals 17:446-453, 1987). Fully 45% of the surveyed adult population of Alachua County, Florida, reported trouble getting to sleep or staying asleep (Karacan et al., Social Science and Medicine 10:239-244, 1976). The prevalence of insomnia has also been shown to be related to the age and sex of the individuals, being higher in older individuals and in females.
Early treatments for insomnia commonly employed central nervous system (CNS) depressants such as barbiturates. These compounds are typically long acting (on the order of 8-50 hours) due to long terminal half-lives, and have a well-known spectrum of side effects, including lethargy, confusion, depression and next day hangover effects. In addition, chronic use has been associated with a high potential for addiction involving both physical and psychological dependence.
During the 1980""s, the pharmaceutical treatment of insomnia shifted away from barbiturates and other CNS depressants toward the benzodiazepine class of sedative-hypnotic agents. This class of compounds produces a calming effect that results in a sleep-like state in humans and animals, with a greater safety margin than prior hypnotics. The therapeutic actions of benzodiazepines are believed to be mediated by binding to a specific receptor on benzodiazepine GABA complexes in the brain. As a result of this binding, synaptic transmission is altered at neurons containing the benzodiazepine GABA complex. The clinical usefulness of different benzodiazepine hypnotics relates largely to their pharmacokinetic differences with regard to this binding and, in particular, to the half-lives of the parent compound and its active metabolites. However, many benzodiazepines possess side effects that limit their usefulness in certain patient populations. These problems include synergy with other CNS depressants (especially alcohol), the development of tolerance upon repeat dosing, rebound insomnia following discontinuation of dosing, hangover effects the next day and impairment of psychomotor performance and memory. Next day sleepiness and memory impairment, which can include amnesia for events occurring prior to and after drug administration, is of particular concern in the elderly whose cognitive functions may already be impaired by the aging process.
More recent treatments for insomnia have used non-benzodiazepine compounds, which show an improved side effect profile over the benzodiazepine class of sedative-hypnotics. The first of these agents to be approved by the United States Food and Drug Administration (FDA) for marketing in the United States was Ambien (zolpidem), which is based on the imidazopyridine backbone (see U.S. Pat. Nos. 4,382,938 and 4,460,592). In addition to Ambien, another compound known as Sonata (zaleplon), which is a pyrazolopyrimidine-based compound (see U.S. Pat. No. 4,626,538), was recently approved by the FDA. Other non-benzodiazepine compounds and/or methods for making or using the same have also been reported (see, e.g., U.S. Pat. Nos. 4,794,185, 4,808,594, 4,847,256, 5,714,607, 4,654,347; 5,538,977, 5,891,891). Attempts have also been disclosed to provide controlled-release dosage forms, particularly in the context of zolpidem and salts thereof (see WO 00/33835 and EP 1 005 863 A1).
Accordingly, there is a need in the art for sedative-hypnotic compositions that induce and maintain sleep as single dose nocturnal formulations, but without the side effects associated with the longer acting hypnotics. The present invention fulfills this need and further provides other related advantages.
Briefly stated, the present invention provides compositions and methods for promoting sleep. Within one aspect, the present invention provides a controlled-release formulation, comprising (a) a sedative-hypnotic compound, or a precursor thereof that is metabolized to generate a sedative-hypnotic compound in vivo, and (b) at least one release retardant such that, upon administration of the formulation to a patient, the patient has a xe2x80x9cpulsedxe2x80x9d plasma profile of the sedative-hypnotic compound. As used herein, a xe2x80x9cpulsedxe2x80x9d plasma profile means that, following administration of the sedative-hypnotic formulation the patient has in the following order:
(i) a time to a first maximum plasma concentration (Tmax1) of the sedative-hypnotic compound ranging from 0.1 to 2 hours following administration;
(ii) a time to a minimum plasma concentration (Tmin) of the sedative-hypnotic compound ranging from 2 to 4 hours, wherein the plasma concentration of the sedative-hypnotic compound at Tmin is less than 80% of the plasma concentration at Tmax1, with the proviso that, in a preferred embodiment, the plasma concentration of the sedative-hypnotic compound at Tmin does not fall below a minimum effective concentration to maintain sleep;
(iii) a time to a second maximum plasma concentration (Tmax2) of the sedative-hypnotic ranging from 3 to 5 hours following administration, wherein the plasma concentration of the sedative-hypnotic compound at Tmax2 is from 80% to 150% of the plasma concentration at Tmax1;
(iv) a plasma concentration of the sedative-hypnotic compound at 6 hours following administration of at least 20% of the plasma concentration at Tmax2; and
(v) a plasma concentration of the sedative-hypnotic compound at 8 hours following administration of no more than 20%, and preferably no more than 15%, of the plasma concentration at Tmax2.
Sedative-hypnotic compounds of this invention have particularly short plasma half-livesxe2x80x94that is, less than 2 hours and, more preferably, on the order of about 1 hour. A representative sedative-hypnotic compound is N-methyl-N-(3-{3-[2-thienylcarbonyl]-pyrazolo-[1,5-a]-pyrimidin-7-yl}-phenyl)acetamide (also referred to herein as xe2x80x9cNBI-34060xe2x80x9d). Representative release retardants include, but are not limited to, hydroxypropylmethyl cellulose, ethyl cellulose, poly (ethylacrylate methylmethacrylate), methacrylic acid copolymer (Type A, Type B, Type C), hydroxypropyl cellulose, carbomer, polyethylene glycol, polyvinylpyrrolidone, gelatin, corn starch, stearyl alcohol, carnuba wax, white wax, glyceryl monostearate, glyceryl distearate, guar gum, xanthan gum and chitosan.
Within further aspects, the present invention provides methods for promoting sleep in a mammal, including a human (collectively referred to herein as a xe2x80x9cpatientxe2x80x9d) and particularly in the context of treating chronic insomnia, comprising administering to a patient a controlled-release formulation as described above. Such formulations may, for example, be administered orally, or by any other route that provides a plasma profile as described herein, and have been found to minimize next day residual effects.
These and other aspects of the present invention will become apparent upon reference to the following detailed description and attached drawings.